When an ingress protection (“IP”) sealed enclosure rapidly transitions from a warm humid environment to a cold, low humidity environment, the moisture in the air volume within the enclosure will condense on the inside surfaces of the enclosure, as these surfaces rapidly cool. This causes problems for a handheld computer used in such situations, which includes windows which need to be free from condensation for a scanner, imager, camera or display to be useable. While this problem has been solved in the past by the use of desiccant packs within the housing, which are used to remove the moisture from the internal air volume, therefore reducing the amount of moisture available to condense on the windows, there are numerous problems with such desiccant packs. Even an IP sealed housing exchanges a small amount of air with the ambient environment by a number of means, which will introduce more moisture into the internal volume, eventually saturating the desiccant pack. For example, once the desiccant pack is saturated, this is detected by the fact that the windows in the housing start to “Fog up” when the handheld transitions from warm to cold environments, which is inconvenient and can lead to failures of the device in the field. While humidity detectors can be used to detect saturated desiccant packs, this can lead to significant product bill of material (“BOM”) cost and complexity increases in design and manufacturing for the handheld. In addition, once the desiccant pack is saturated, the handheld needs to be serviced, to replace the desiccant pack, which means that the handheld needs to be taken out of service. Also, careful handling of the replacement desiccant pack is required during the service procedure, because if the desiccant pack is exposed to the ambient environment for too long, its useful life may be significantly reduced as it absorbs moisture from the ambient environment.
Furthermore, when an IP sealed enclosure is dropped or otherwise abused, the integrity of the seal can become compromised. When the IP seal is compromised, a range of equipment failures can occur, as the ambient environment leaks into the enclosure. A compromised IP seal can be detected indirectly, when the equipment is in the field, as the equipment fails due to the ingress of the ambient environment. While it is possible to detect a compromised IP seal by performing a vacuum test on the enclosure, to detect leaks in the IP seal, this requires costly equipment which is not commonly available at customer sites.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.